Micromachined biocompatible catheter flow sensor with trench structure

We developed a catheter flow sensor based on biocompatible parylene HT® film and introduce a trench structure around the heater to reduce the response time. We evaluated both vertical- and undercut-etching-rates of the parylene HT® film by oxygen dry etching to produce a trench on the film and confirmed that it was anisotropically etched with a ratio of 4.8 (vertical/undercut directions). The catheter flow sensor with the trench around the heater was produced by adding the dry etching step to the photolithography, metal deposition, and heat-shrinkable package processes. Thanks to the trench formation around the heater, the response times drastically reduced to less than one-half that of the un-trenched sensor.